As part of an interview with Billboardfor the magazine's April 2 cover story, Cowell, who's worked with 1D since they appeared as independent acts on X Factor in 2010, said he's not sure the group's current hiatus has an expiration date.

"I don't know if it's a hiatus or a breakup, to be honest," Cowell said. "In a weird way, I don't want to know. I don't think they've had enough time to experience what it's like not being in the group to really answer that."

"Whenever I was with them, we talked about [the hiatus], and I couldn’t argue with them," he added. "They had achieved so much in a short period of time, and I didn’t want them to get jaded. As I’ve gotten older, I’ve learned to trust people more, particularly artists. They’ll decide when they want to come back together."

That recent trust considered, Cowell jokingly recalled One Direction being "a nightmare" to work with upon their initial signing to Syco.

"They were like five puppies — really excited, loads of opinions, always wanted to hang out," he said.

Louis Tomlinson, who told Billboard Cowell is trustworthy and "lovely and kind," said the exec's treatment of One Direction over the years — especially toward the beginning of the guys' careers — is a true reflection of his gentle temperament.

"We were at the height of our immaturity, always running around and being mischievous," Tomlinson said. "There were so many meetings where Simon had to snap us to attention, but he was very patient."